This invention relates generally to vision systems and, more particularly, to a method and system for displaying an image.
During daylight hours, the driver of a vehicle is able to detect and recognize objects that would be difficult, if not impossible, to detect or recognize at night. For example, on a sunny day, a deer approximately 500 meters ahead of a vehicle should be readily detectable and recognizable. At night, however, particularly when the headlights provide the only illumination, the deer will not be detectable, much less recognizable, at that distance because it will be beyond the range of the headlights. Moreover, by the time the driver detects the deer, and well before recognizing what it is, the vehicle will be much closer to the deer than during daylight. Accordingly, the risk of a resulting accident is much higher at night than during the day.
Consequently, in order reduce the risk of accidents, night vision systems have been developed to supplement the driver""s vision. One example of a night vision system is included in U.S. Pat. No. 5,781,243 entitled xe2x80x9cDisplay Optimization for Night Vision Enhancement Systems.xe2x80x9d Some night vision systems include an infrared camera unit mounted in the grill of the vehicle and an image source mounted in the vehicle""s dashboard. The camera unit gathers information regarding the scene in front of the vehicle, and the image source projects an image derived from the information onto the windshield for display.
Using the windshield for image display, however, has several drawbacks. For example, the illumination of the image may be poor because a large amount of light is lost due to refraction. As another example, the image may be distorted because of the windshield""s varying curvature. To address these drawbacks, several night vision systems are proposing to use a magnifying optical element mounted to the dashboard as a display device for the driver. Because of vision and aesthetic considerations, there is a continuing demand to reduce the size of the display device. Typical displays provide excess information which may confuse the driver. For example, the excess information may distort the depth perception of the driver, particularly when the image displayed for the driver is one that has been minified.
The present invention provides a method and system for displaying an image that substantially eliminates or reduces at least some of the disadvantages and problems associated with previous methods and systems.
In accordance with a particular embodiment of the present invention, a method for displaying an image includes selecting a camera unit horizontal field of view (FOV) of about eighteen degrees and selecting a system magnification of between 0.4 and 1.0. The method also includes determining an aspect ratio for the image based on the selected camera unit horizontal FOV and the selected system magnification, receiving energy from a scene for forming the image and displaying the image on a display.
The selected horizontal FOV may comprise eighteen degrees, and the system magnification may comprise approximately 0.55. The determined aspect ratio for the image may comprise approximately 10:3.3 or 3.1. The method may also include converting the energy received into information representative of the received energy and forming the image using the information representative of the received energy. Displaying the image on a display may comprise projecting the image onto a fold mirror and reflecting the visible image to an imaging mirror using the fold mirror.
In accordance with another embodiment, a system for displaying an image includes a camera unit having a horizontal FOV selected to be about eighteen degrees and a system magnification selected to be between 0.4 and 1.0. The system includes a display coupled to the camera unit. The display is operable to display the image. The image has an aspect ratio determined based on the selected camera unit horizontal FOV and the selected system magnification.
The system may further include a lens system operable to direct energy from a scene toward a detector and a display unit comprising the display. The display unit may be coupled to the detector and may be operable to form the image using information received from the detector. The detector may include an array of detector elements, each detector element operable to receive energy from a portion of the scene and to convert the received energy into information representative of the received energy and to send the information associated with at least some of the detector elements to the display unit. The display unit may comprise a liquid crystal display (LCD) operable to project the image onto a fold mirror. The fold mirror may be configured to reflect the visible image to an imaging mirror.
Technical advantages of particular embodiments of the present invention include an auxiliary vision system having a camera unit with a horizontal FOV of about eighteen degrees, a selected system magnification of approximately 0.4 to 1.0 and an aspect ratio determined based on the system magnification and the horizontal FOV of the camera unit. Such a system is particularly suited to present an auxiliary image that better enables a driver to properly perceive depth in the image. Furthermore, the horizontal FOV of the camera unit of about eighteen degrees presents a beneficial amount of horizontal information to the driver to effectively see potential hazards in the roadway in front of the vehicle, especially in combination with a system magnification selected between 0.4 and 1.0 and a displayed image aspect ratio based on such camera unit horizontal FOV and selected system magnification. Moreover, this horizontal FOV of the camera unit coupled with a selected magnification of between 0.4 and 1.0 can more effectively be utilized and packaged in an auxiliary vehicle system.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.